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/**
 * @file atmosphere.cpp
 *
 */

#include <geo/geo.h>
#include "atmosphere.h"
namespace atmosphere
{


float getDensityFromPressureAndTemp(const float pressure_pa, const float temperature_celsius)
{
	return (pressure_pa / (kAirGasConstant * (temperature_celsius - kAbsoluteNullCelsius)));
}
float getPressureFromAltitude(const float altitude_m)
{

	return kPressRefSeaLevelPa * powf((altitude_m * kTempGradient + kTempRefKelvin) / kTempRefKelvin,
					  -CONSTANTS_ONE_G / (kTempGradient * kAirGasConstant));
}
float getAltitudeFromPressure(float pressure_pa, float pressure_sealevel_pa)
{
	// calculate altitude using the hypsometric equation

	const float pressure_ratio = pressure_pa / pressure_sealevel_pa;

	/*
	 * Solve:
	 *
	 *     /        -(aR / g)     \
	 *    | (p / p1)          . T1 | - T1
	 *     \                      /
	 * h = -------------------------------  + h1
	 *                   a
	 */
	return (((powf(pressure_ratio, (-(kTempGradient * kAirGasConstant) / CONSTANTS_ONE_G))) * kTempRefKelvin) -
		kTempRefKelvin) / kTempGradient;

}
float getStandardTemperatureAtAltitude(float altitude_m)
{
	return 15.0f + kTempGradient * altitude_m;
}
}
